For industrial gas turbine systems, an air intake chamber is provided that includes a large number of tubular filters. Each filter has a closed end facing the inlet to the chamber, and an open end attached to the outflow section of the chamber. The air passes into the filter through the filter's porous cylindrical side and then out of the filter's open end to the outflow section of the chamber.
In the conventional design, a “pre-filter wrap” is provided, which is a sheet of porous material that is wrapped around the exterior of the filter to act as a first, coarse filter to prevent coarse or large debris from entering or attaching to the filter. This lengthens the life of the filters and prevents penetration of large debris through the filter that could damage the turbine or other device.
In such intake filtration chambers, however, the large number of cylindrical filters in the chamber are frequently so close to each other that it makes it very difficult to wrap or unwrap the pre-filter wraps around the filter in a circular motion to completely cover the cylindrical side of the filter. This awkward motion increases the time, and therefore the labor cost to maintain the filters.
Taking the filters out of a filtering position in the intake chamber to change the pre-filter wrap, however, is undesirable when the filtration is being performed on an air intake pipe or duct for a turbine or other device that must be operational at all times (“continuous operation”) and does not have scheduled down times for maintenance when the filters can be changed. Permitting ambient air to enter the out flow duct section or duct through an unfiltered space while the pre-filter wrap is being changed may permit large debris to enter the air flow duct and subsequently damage or jam the motor or other device being protected.
In addition, the conventional pre-filter wrap has an openable, longitudinal seal, sealed by a clasping, sticking or hook-and-loop material such as VELCRO®, which frequently results in spaces throughout the seal for large debris to bypass the outer pre-filter wrap and be trapped by the primary filter, which reduces the service life of the primary filter.